The present invention relates generally to a method of making a heat exchanger and to the resultant heat exchanger. More particularly, it relates to a finned type heat exchanger and evaporator produced by inserting a serpentine tube bundle into a plurality of inner fins retained in a fixture at a staggered arrangement in which an interference fit between the inner fins and the tube bundle retains the inner fins onto the tube bundle and then removing the tube bundle with the inner fins attached from the fixture. The resultant evaporator comprises a serpentine tube bundle having a plurality of inner fins attached thereon wherein the inner fins are off-set to provide a staggered inner fin pattern.
Finned type heat exchangers are commonly used in a variety of heat exchanger-type apparatus. Finned heat exchangers having a tube bundle of a serpentine arrangement and fins mounted on the tubes are used in condensers and evaporators of refrigeration units, air conditioning units and the like. The fins are attached to the tube bundle and increase the effective heat absorbing area over which air flow is directed, thus increasing the cooling efficiency of the evaporator.
Several attempts have been made to increase the cooling efficiency of the evaporator by varying the arrangement of the tube pattern and fin shape. U.S. Pat. No. 4,580,623 discloses a heat exchanger having parallel rows of serpentine tube coils slanted in the same direction and using ultra thin fins having a pattern embossed thereon to induce turbulence in the air flow over the evaporator.
Another method of arranging the serpentine tube coils to increase the cooling efficiency of the evaporator is described in U.S. Pat. No. 5,183,105. This construction has a continuous tube with a plurality of reverse bends forming a plurality of parallel tube rows arranged in sets of two as determined by each of the respective-reverse bends. The tubes in the tube bundle are arranged such that, when viewed in cross section, lines drawn between the centers of the sets of two tubes form a herringbone pattern.
While these methods increase the cooling efficiency of the evaporator by using the staggered arrangement of the tube bundle, further cooling efficiency can be obtained by a more efficient arrangement of the fins.
The present invention is directed to a method of making an evaporator and to the resultant evaporator. The evaporator comprises a continuous serpentine tube having an inlet and an outlet. The serpentine tube includes at least one column of parallel tube runs. Each tube run is defined by at least one reverse bend. The column of parallel tube runs has an overall length defined by the distance between the outermost tube runs. The evaporator further comprises a plurality of inner fins attached to the individual tubes. Each inner fin extends between two tube runs defined by opposite ends of a reverse bend. The inner fins have a length less than the overall length the column of tube runs.